Can't resize VM

[Kiasta]

I can't get a widescreen resolution for some reason. I have 2 monitors setup: the monitor VirtualBox is on has a max resolution of 1366x768 and the main Monitor is 1680x1050(not sure it matters). Everything I've installed I cannot get the resolution past 1024x768 I've tried Linux Mint 16 and Ubuntu 13.10 and now I have windows 8.1 running but still stuck at 1024x768. I clicked the Insert Guest Additions CD Image but nothing happens (for any of the OSs). I've tried to re-size the window and I've tried to stretch the window but nothing seems to work, inside the VM 1024x768 is always the max resolution. Any suggestions? Am I not doing something right because I have no problem with the resolution using VMWare but VMWare crashes all the time and the sound never worked, VirtualBox has always been stable and has never crashed but the resolution problem is a real bummer. In fullscreen mode I get borders on the sides and I even took an SS. Any information you need about my computer I'll give it but like I said I was able to get full 1366x768 resolution in VMWare.

System Specs:
Base Memory: 2048MB
Acceleration: VT-x/AMD-V, Nested Paging (not sure if this matters, but here it is anyway)
Video Memory 128MB (but inside the VM it shows 0MB of Dedicated VRAM and 256MB of shared)

i(dot)imgur(dot)com/WRKZxCN(dot)png (apparently I can't post links because I'm too new...)

[Perryg]

Inserting the guest additions mounts them to the virtual CD. Open it in the guest and run the install.

[Kiasta]

Thanks, I didn't realize there was an ISO I was supposed to download.

Is there an option to remove this black background? It seems like it is a placeholder (probably should be transparent) for the VirtualBox Control Panel. Nothing I've tried seems to work. Leaving/entering fullscreen, rebooting VM, rebooting guest, etc. Is there an option I'm missing in the settings menu? I took a picture with my cell phone to show you.

i(dot)imgur(dot)com/lUh9ioa(dot)jpg

[Kiasta]

I disabled 3D Acceleration and that seemed to do the trick.